Wednesday, December 22, 2010

Avoid Getting Washed Away

There's a lot of concern about floods and mudslides right now in about half dozen of the western states. Governors are filing for "state of emergency" federal funds, officials are ordering evacuations, people are losing their homes, and some are losing their lives.

Flooding is a huge problem that can lead to both urban and backcountry survival situations. According to national statistics, flooding is the leading cause of weather-related deaths in the U.S., killing, on average, about two hundred people each year. Two hundred per year might not sound like a lot, until you compare that number with the average statistics for hurricane-related deaths (24), or tornadoes (69), or lightning strikes (81).

One of the deadliest flash floods in U.S. history swept down Colorado’s Big Thompson Canyon during the height of the 1976 summer tourist season. People were trying to escape Denver’s city heat by going to a popular camping area, where the temperatures were cooler and the day was perfect. As it turned out, the day was perfect for an unusual combination of atmospheric conditions to join forces, with deadly results. Afternoon heat created powerful updrafts that carried moist air aloft, and when that air reached the cooler upper atmosphere, it didn’t take long for a thunderstorm to form.

Heavy rain began to fall in the mountains above Big Thompson Canyon. Normally, thunderstorms move fairly rapidly across the landscape, being pushed across the countryside by strong winds. But this one didn’t. It just sat there and dumped. Three hours later, more than a foot of rain had fallen, with eight inches falling during one intense hour-long cloudburst.

The stream grew from its normally placid 2-foot-deep trickle to a violent killer that was 19 feet high and raging through the canyon, wickedly propelling 10-foot boulders and broken trees that had been ripped out of the ground. In a heartbeat, everything was gone — vehicles, buildings, and people. The crushing flood swept through the canyon with such speed and violence that it was impossible to out-run. Buildings and vehicles instantly became death traps, and there was no possible avenue of escape, except straight up the canyon walls. Two hours later, the death toll was 145, including 6 people who were never found.

The trouble with flash floods is that they arrive unannounced, and they often come from many miles away. It might not even be raining where you are, but twenty miles away a cloudburst can set things in motion and a few hours later the flood sweeps you and your camp away in a raging torrent.

Flash floods feed on three things — heavy rainfall (or perhaps sudden snowmelt), a system of drainages or lowlands where the water collects and funnels downstream, and time. A ten-minute monsoon isn’t going to create much of a flood but one that lasts an hour and dumps several inches of water will.

Soil that doesn’t absorb moisture easily is a huge contributor. And if the area is denuded of vegetation by fire, timber harvest or other land clearing operations, the problem is made worse. The brushfires that denuded hillsides over the last few years are a major factor in the flooding and mudslides now ripping up southern California.

There is literally no region that is safe from the possibility of flash flood — deserts, mountains and plains are all vulnerable areas.

Flash floods are sneaky — they seem to come out of nowhere. There could be a violent thunderstorm taking place farther back in the mountains or on a distant desert plateau — a downpour might be hitting the rocky ground and funneling runoff into a drainage that eventually leads to your location. You might have no clue a deadly flash flood is roaring toward you like a liquid freight train until you hear the approaching rumble, feel the ground tremble, and suddenly see a wall of water carrying trees and boulders through your camp.

So you need to have a survival plan, just in case you find yourself in the wrong place on the wrong day.

Preventive Planning

Listen to the weather forecast before heading out. If the forecast talks about unstable air, thunderstorms or other violent weather, don’t go into places where a flash flood might catch you.

Periodically monitor the NOAA Weather Radio station in your area to learn if there are weather events taking place that will affect you. You can buy a fairly inexpensive and compact, battery-operated weather radio at places like Radio Shack.

If Flood Advisories, Warnings or Watches are issued, heed them.

When you arrive in camp, look the situation over and imagine what the place would look like if it were suddenly swept by a 30-foot wall of water (yes, they get that big). Choose a campsite that is above the danger zone. Don’t camp in lowlands or even in a minor drainage.

Surviving a Flash Flood

Get to higher ground immediately. The water level might rise incredibly fast.

Don’t stop to gather up your equipment. Saving your life (and the lives of others) is more important than saving your vehicle or other gear.

If you are trapped by floodwaters that are surrounding your vehicle, get out immediately and make your way to higher ground. It takes only 2 feet of water to sweep away a vehicle, and it will roll and tumble and smash as it is swept downstream. A vehicle is not a safe place to be. Approximately half of flood-related drownings are vehicle-related.

Do not attempt to drive across a flooded road. What you can’t see is that the roadway might have been ripped up by the rushing water, leaving a hole that will swallow your vehicle.

If you recognize the potential danger of a flash flood, take steps to keep yourself, your friends and loved-ones safe during your travels and camping trips.

3 comments:

I gets mighty wet in my yard during heavy rains but because of where I live flooding isn't an issue. Before it floods here a large part of the town will be in trouble also and I'm on a large enough gently sloping area that the place isn't likely to go sliding downhill.

But just in case, I have three boats, crazy guys like to be prepared for everything.

Perfect timing Rich, thanks again for running this site and posting so much accurate and usable info. I am forwarding this page to a friend of mine who called me yesterday to tell me that earlier that day she had been trapped in her car with 21 other vehicles who were hit by a relatively small flash flood in San Bernardino, CA, yesterday. Thankfully in this instance there was no loss of life but they were stranded in their vehicles until the local fire dept arrived. She called me later to find out what she should have done and I directed her to your site. I just wanted to let you know that your website helps save lives. Thank you for keeping this up and running and I will continue to check it weekly. Sincerely, Clem

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My career has focused on wilderness survival, urban survival, and surviving catastrophic disasters.
After serving in Special Forces, I took our family to live in a cave in the wilds of southern Utah, while I prepared to become a survival instructor. We spent a year in the wilderness, experiencing all sorts of shelters, and making full use of the natural resources.
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